This invention relates to systems and methods for processing blood, e.g., for filtration, pheresis, or other diagnostic or therapeutic purposes.
There are many types of continuous and intermittent blood processing systems, each providing different therapeutic effects and demanding different processing criteria.
For example, hemofiltration emulates normal kidney activities for an individual whose renal function is impaired or lacking. During hemofiltration, blood from the individual is conveyed in an extracorporeal path along a semipermeable membrane, across which a pressure difference (called transmembrane pressure) exists. The pores of the membrane have a molecular weight cut-off that can thereby pass liquid and uremic toxins carried in blood. However, the membrane pores can not pass formed cellular blood elements and plasma proteins. These components are retained and returned to the individual with the toxin-depleted blood. Membranes indicated for hemofiltration are commercially available and can be acquired from, e.g., Asahi Medical Co. (Oita, Japan).
After hemofiltration, fresh physiologic fluid is supplied to toxin-depleted blood. This fluid, called replacement fluid, is buffered either with bicarbonate, lactate, or acetate. The replacement fluid restores, at least partially, a normal physiologic fluid and electrolytic balance to the blood. Usually, an ultrafiltration function is also performed during hemofiltration, by which liquid is replaced in an amount slightly less than that removed. Ultrafiltration decreases the overall fluid level of the individual, which typically increases, in the absence of ultrafiltration, due to normal fluid intake between treatment sessions.
Following hemofiltration, fluid balancing, and ultrafiltration, the blood is returned to the individual.
The invention provides systems and methods for carrying out hemofiltration. The systems and methods establish an extracorporeal fluid circuit that communicates with hemofilter. The circuit defines within a flexible panel a flow channel that is free of an air interface. The flexible panel includes an in-line sensor region through which fluid pressure in the flow channel can be measured by an external sensor. The systems and methods enable sensing fluid pressure through the in-line sensor region using the external sensor.
The flow channel can convey, e.g., waste from the hemofilter or replacement fluid for return to the individual.
In one embodiment, the systems and methods pump fluid in the flow channel by externally applying peristaltic pressure to the flexible panel. The systems and methods can sense fluid pressure either downstream of where peristaltic pressure is applied or upstream of where peristaltic pressure is applied.
In one embodiment, the systems and methods occlude the flow channel by externally applying force to the flexible panel.
Other features and advantages of the inventions are set forth in the following specification and attached drawings.